Whitepaper

Near Field Probe for Detecting Resonances in EMC Application

Published by Amber Precision Instruments

This paper proposes a novel near-field probe that integrates an electrically small metallic cone with a shielded magnetic loop to detect resonances in PCBs, cables, and structural elements. The E-field from the cone dominates coupling; S21 measurements between the two ports reveal resonant structures when S21 rises above the baseline. Validated in CST and HFSS and demonstrated on a ring microstrip test structure (resonance at ~240 MHz) and a computer motherboard (cable resonance at ~109 MHz), the probe integrates into automated scanning systems without requiring 90° rotation, enabling spatial mapping of resonance frequencies and Q-factors.